Process for the preparation of 1,3,3,3-tetrafluoropropene and/or 2,3,3,3-tetrafluoropropene

ABSTRACT

A process for the manufacture of CF 3 CH═CHF and/or CF 3 CF═CH 2  is disclosed. The process involves (a) reacting HF and chlorine and at least one halopropene of the formula CX 3 CCI═CCIX (where each X is independently F or Cl) to produce a product including both CF 3 CCI 2 CCIF 2  and CF 3 CCIFCCI 2 F; (b) reacting CF 3 CCI 2 CCIF 2  and CF 3 CCIFCCI 2 F produced in (a) with hydrogen to produce a product including both CF 3 CH 2 CHF 2  and CF 3 CHFCH 2 F; (c) dehydrofluorinating CF 3 CH 2 CHF 2  and CF 3 CHFCH 2 F produced in (b) to produce a product including both CF 3 CH═CHF and CF 3 CF═CH 2 ; and (d) recovering CF 3 CH═CHF and/or CF 3 CF═CH 2  from the product produced in (c). In (a), both CF 3 CCI 2 CCIF 2  and CF 3 CCIFCCI 2 F are produced in the presence of a chlorofluorination catalyst consisting of (i) compositions comprising a crystalline alpha-chromium oxide where at least 0.05 atom % of the chromium atoms in the alpha-chromium oxide lattice are replaced by copper, and (ii) compositions of (i) which have been treated with a fluorinating agent.

FIELD OF THE INVENTION

This invention relates to the synthesis of 1,3,3,3-tetrafluoropropeneand 2,3,3,3-tetrafluoropropene.

BACKGROUND

A number of chlorine-containing halocarbons are considered to bedetrimental toward the Earth's ozone layer. There is a worldwide effortto develop materials having lower ozone depletion and global warmingpotential that can serve as effective replacements. For example, thehydrofluorocarbon, 1,1,1,2-tetrafluoroethane (HFC-134a) is being used asa replacement for dichlorodifluoromethane (CFC-12) in refrigerationsystems. HFC-134a has a high global warming potential. There is a needfor manufacturing processes that provide halogenated hydrocarbons thathave lower ozone depletion and global warming potential. The productionof hydrofluoroolefins (i.e., unsaturated compounds containing onlycarbon, hydrogen and fluorine), has been the subject of recent interestto provide environmentally desirable products for use as refrigerants,solvents, blowing agents, cleaning agents, aerosol propellants, heattransfer media, dielectrics, fire extinguishants, power cycle workingfluids and polymer intermediates. For example,1,3,3,3-tetrafluoropropene and 2,3,3,3-tetrafluoropropene have utilityin such applications and as starting materials for the synthesis ofother fluorinated molecules.

SUMMARY OF THE INVENTION

This invention provides a process for the manufacture of1,3,3,3-tetrafluoropropene (CF₃CH═CHF, HFC-1234ze) and/or2,3,3,3-tetrafluoropropene (CF₃CF═CH₂, HFC-1234yf). The processcomprises (a) reacting hydrogen fluoride (HF), chlorine (Cl₂), and atleast one halopropene of the formula CX₃CCl═CClX, wherein each X isindependently selected from the group consisting of F and Cl, to producea product comprising CF₃CCl₂CClF₂ and CF₃CClFCCl₂F, wherein saidCF₃CCl₂CClF₂ and CF₃CClFCCl₂F are produced in the presence of achlorofluorination catalyst comprising at least one chromium-containingcomponent selected from (i) a crystalline alpha-chromium oxide where atleast 0.05 atom % of the chromium atoms in the alpha-chromium oxidelattice are replaced by divalent copper, and (ii) a chromium-containingcomposition of (i) which has been treated with a fluorinating agent(e.g., anhydrous hydrogen fluoride); (b) reacting CF₃CCl₂CClF₂ andCF₃CClFCCl₂F produced in (a) with hydrogen (H₂) to produce a productcomprising CF₃CH₂CHF₂ and CF₃CHFCH₂F; (c) dehydrofluorinating CF₃CH₂CHF₂and CF₃CHFCH₂F produced in (b) to produce a product comprising CF₃CH═CHFand CF₃CF═CH₂; and (d) recovering CF₃CH═CHF and/or CF₃CF═CH₂ from theproduct produced in (c).

DETAILED DESCRIPTION

This invention provides a process for the manufacture of CF₃CH═CHF(HFC-1234ze) that can be present as the E- and Z- forms of isomers, andCF₃CF═CH₂ (HFC-1234yf). The HFC-1234ze and HFC-1234yf may be recoveredas individual products and/or as one or more mixtures of the twoproducts.

In step (a) of the process of this invention, one or more halopropenecompounds CX₃CCl═CClX, wherein each X is independently selected from thegroup consisting of F and Cl, are reacted with chlorine (Cl₂) andhydrogen fluoride (HF) to produce a product mixture comprisingCF₃CCl₂CClF₂ (CFC-215aa) and CF₃CClFCCl₂F (CFC-215bb). Accordingly, thisinvention provides a process for the preparation of mixtures ofCF₃CCl₂CClF₂ (CFC-215aa) and CF₃CClFCCl₂F (CFC-215bb) from readilyavailable starting materials.

Suitable starting materials for the process of this invention include E-and Z-CF₃CCl═CClF (CFC-1214xb), CF₃CCl═CCl₂ (CFC-1213xa), CClF₂CCl═CCl₂(CFC-1212xa), CCl₂FCCl═CCl₂ (CFC-1211 xa), and CCl₃CCl═CCl₂(hexachloropropene, HCP), or mixtures thereof.

Due to their availability, CF₃CCl═CCl₂ (CFC-1213xa) and CCl₃CCl═CCl₂(hexachloropropene, HCP) are the preferred starting materials for theprocess of the invention.

Preferably, the reaction of HF and Cl₂ with CX₃CCl═CClX is carried outin the vapor phase in a heated tubular reactor. A number of reactorconfigurations are possible, including vertical and horizontalorientation of the reactor and different modes of contacting thehalopropene starting material(s) with HF and chlorine. Preferably the HFand chlorine are substantially anhydrous.

In one embodiment of step (a), the halopropene starting material(s) arefed to the reactor contacting the chlorofluorination catalyst. Thehalopropene starting material(s) may be initially vaporized and fed tothe first reaction zone as gas(es).

In another embodiment of step (a), the halopropene starting material(s)may be contacted with HF in a pre-reactor. The pre-reactor may be empty(i.e., unpacked), but is preferably filled with a suitable packing suchas Monel™ or Hastelloy™ nickel alloy turnings or wool, or other materialinert to HCl and HF which allows efficient mixing of CX₃CCl═CClX and HFvapor.

If the halopropene starting material(s) are fed to the pre-reactor asliquid(s), it is preferable for the pre-reactor to be orientedvertically with CX₃CCl═CClX entering the top of the reactor andpre-heated HF vapor introduced at the bottom of the reactor.

Suitable temperatures for the pre-reactor are within the range of fromabout 80° C. to about 250° C., preferably from about 100° C. to about200° C. Under these conditions, for example, hexachloropropene isconverted to a mixture containing predominantly CFC-1213xa. Thefeed-rate of starting material is determined by the length and diameterof the pre-reactor, the pre-reactor temperature, and the degree offluorination desired within the pre-reactor. Slower feed rates at agiven temperature will increase contact time and tend to increase theamount of conversion of the starting material and increase the degree offluorination of the products.

The term “degree of fluorination” means the extent to which fluorineatoms replace chlorine substituents in the CX₃CCl═CClX startingmaterials. For example, CF₃CCl═CClF represents a higher degree offluorination than CClF₂CCl═CCl₂ and CF₃CCl₂CF₃ represents a higherdegree of fluorination than CClF₂CCl₂CF₃.

The molar ratio of HF fed to the pre-reactor, or otherwise to thereaction zone of step (a), to halopropene starting material fed in step(a), is typically from about stoichiometric to about 50:1. Thestoichiometric ratio depends on the average degree of fluorination ofthe halopropene starting material(s) and is typically based on formationof C₃Cl₃F₅. For example, if the halopropene is HCP, the stoichiometricratio of HF to HCP is 5:1; if the halopropene is CFC-1213xa, thestoichiometric ratio of HF to CFC-1213xa is 2:1. Preferably, the molarratio of HF to halopropene starting material is from about twice thestoichiometric ratio (based on formation of C₃Cl₃F₅) to about 30:1.Higher ratios of HF to halopropene are not particularly beneficial.Lower ratios result in reduced yields of C₃Cl₃F₅ isomers.

If the halopropene starting materials are contacted with HF in apre-reactor, the effluent from the pre-reactor is then contacted withchlorine in the reaction zone of step (a).

In another embodiment of step (a), the halopropene starting material(s)may be contacted with Cl₂ and HF in a pre-reactor. The pre-reactor maybe empty (i.e., unpacked) but is preferably filled with a suitablepacking such as Monel™ or Hastelloy™ nickel alloy turnings or wool,activated carbon, or other material inert to HCl, HF, and Cl₂ whichallows efficient mixing of CX₃CCl═CClX, HF, and Cl₂.

Typically at least a portion of the halopropene starting material(s)react(s) with Cl₂ and HF in the pre-reactor by addition of Cl₂ to theolefinic bond to give a saturated halopropane as well as by substitutionof at least a portion of the Cl substituents in the halopropropaneand/or halopropene by F. Suitable temperatures for the pre-reactor inthis embodiment of the invention are within the range of from about 80°C. to about 250° C., preferably from about 100° C. to about 200° C.Higher temperatures result in greater conversion of the halopropene(s)entering the reactor to saturated products and greater degrees ofhalogenation and fluorination in the pre-reactor products.

The term “degree of halogenation” means the extent to which hydrogensubstituents in a halocarbon have been replaced by halogen and theextent to which carbon-carbon double bonds have been saturated withhalogen. For example, CF₃CCl₂CClF₂ has a higher degree of halogenationthan CF₃CCl═CCl₂. Also, CF₃CCl₂CClF₂ has a higher degree of halogenationthan CF₃CHClCClF₂.

The molar ratio of Cl₂ to halopropene starting material(s) is typicallyfrom about 1:1 to about 10:1, and is preferably from about 1:1 to about5:1. Feeding Cl₂ at less than a 1:1 ratio will result in the presence ofrelatively large amounts of unsaturated materials andhydrogen-containing side products in the reactor effluent.

In a preferred embodiment of step (a) the halopropene starting materialsare vaporized, preferably in the presence of HF, and contacted with HFand Cl₂ in a pre-reactor and then contacted with the chlorofluorinationcatalyst. If the preferred amounts of HF and Cl₂ are fed in thepre-reactor, additional HF and Cl₂ are not required when the effluentfrom the pre-reactor contacts the chlorofluorination catalyst.

Suitable temperatures for catalytic chlorofluorination of halopropenestarting material and/or their products formed in the pre-reactor arewithin the range of from about 200° C. to about 400° C., preferably fromabout 250° C. to about 350° C., depending on the desired conversion ofthe starting material and the activity of the catalyst. Reactortemperatures greater than about 350° C. may result in products having adegree of fluorination greater than five. In other words, at highertemperatures, substantial amounts of chloropropanes containing six ormore fluorine substituents (e.g., CF₃CCl₂CF₃ or CF₃CClFCClF₂) may beformed. Reactor temperature below about 240° C. may result in asubstantial yield of products with a degree of fluorination less thanfive (i.e., underfluorinates).

Suitable reactor pressures for vapor phase embodiments of this inventionmay be in the range of from about 1 to about 30 atmospheres. Reactorpressures of about 5 atmospheres to about 20 atmospheres may beadvantageously employed to facilitate separation of HCl from otherreaction products in step (b) of the process.

The chlorofluorination catalysts which are used in the process of thepresent invention are compositions comprising crystalline α-Cr₂O₃(α-chromium oxide) in which some of the chromium(III) ions have beensubstituted by copper(II) ions or compositions obtained by treatment ofsaid compositions with a fluorinating agent. Of note are embodimentscontaining at least 1 atom % copper based on the total of the copper andchromium in the alpha-chromium oxide. The amount of copper relative tothe total of chromium and copper in these compositions is preferablyfrom about 1 atom % to about 5 atom %. Of particular note areembodiments containing from about 2 atom % to about 3 atom % copperbased on the total of the copper and chromium in the alpha-chromiumoxide.

These compositions may be prepared, for example, by co-precipitationmethods followed by calcination.

In a typical co-precipitation procedure, an aqueous solution of copperand chromium(III) salts is prepared. The relative concentrations of thecopper and chromium(III) salts in the aqueous solution is dictated bythe bulk atom percent copper relative to chromium desired in the finalcatalyst. Therefore, the concentration of copper in the aqueous solutionis preferably from about 1 atom % to about 5 atom % of the totalconcentration of copper and chromium in the solution. The concentrationof chromium(III) in the aqueous solution is typically in the range of0.3 to 3 moles per liter with 0.75-1.5 moles per liter being a preferredconcentration. While different chromium(III) salts might be employed,chromium(III) nitrate or its hydrated forms such as [Cr(NO₃)₃(H₂O)₉],are the most preferred chromium(III) salts for preparation of saidaqueous solution.

While different copper salts might be employed for preparation of saidaqueous solutions, preferred copper salts for preparation of catalystsfor the process of this invention include copper(II) nitrate and itshydrated forms such as [Cu(NO₃)₂(H₂O)_(2.5)] and copper(II) chloride.

The aqueous solution of the chromium(III) and copper salts may then beevaporated either under vacuum or at elevated temperature to give asolid which is then calcined.

It is preferred to treat the aqueous solution of the chromium(III) andcopper salts with a base such as ammonium hydroxide (aqueous ammonia) toprecipitate the copper and chromium as the hydroxides. Bases containingalkali metals such as sodium or potassium hydroxide or the carbonatesmay be used but are not preferred. The addition of ammonium hydroxide tothe aqueous solution of the chromium(III) and copper salts is typicallycarried out gradually over a period of 1 to 12 hours. The pH of thesolution is monitored during the addition of base. The final pH istypically in the range of 6.0 to 11.0, preferably from about 7.5 toabout 9.0, most preferably about 8.0 to about 8.7. The precipitation ofthe copper and chromium hydroxide mixture is typically carried out at atemperature of about 15° C. to about 60° C., preferably from about 20°C. to about 40° C. After the ammonium hydroxide is added, the mixture istypically stirred for up to 24 hours. The precipitated chromium andcopper hydroxides serve as precursors to the catalysts of the invention

After the precipitation of the copper and chromium hydroxide mixture iscomplete, the mixture is dried. This may be carried out by evaporationin an open pan on a hot plate or steam bath or in an oven or furnace ata suitable temperature. Suitable temperatures include temperatures fromabout 60° C. to about 130° C. (for example, about 100° C. to about 120°C.). Alternatively, the drying step may be carried out under vacuumusing, for example, a rotary evaporator.

Optionally, the precipitated copper and chromium hydroxide mixture maybe collected and, if desired, washed with deionized water before drying.Preferably the precipitated copper and chromium hydroxide mixture is notwashed prior to the drying step.

After the copper and chromium hydroxide mixture has been dried, thenitrate salts are then decomposed by heating the solid from about 250°C. to about 350° C. The resulting solid is then calcined at temperaturesof from about 400° C. to about 1000° C., preferably from about 400° C.to about 900° C.

The copper-substituted alpha-chromium oxide compositions may also beprepared by a thermal method. In this method, a solution of the copperand chromium(III) salts is prepared as described for theco-precipitation technique. The mixed solution of the salts is thenevaporated under atmospheric pressure or reduced pressure to give asolid. The solid is then placed in a furnace and the temperature raisedgradually to decompose the salt. It is preferred to use the nitratesalts that decompose to the oxide. After decomposition of the nitratesalts is complete (about 350° C.), the increase in temperature iscontinued until the desired calcination temperature is reached. Thedesired calcination temperature is between about 450° C. to about 100°C., a temperature of about 450° C. to about 900° C. being preferred.After the desired calcination temperature is reached, the solid ismaintained at this temperature for an additional 8 to 24 hours, about 8to about 12 hours being preferred. The decomposition and calcination ispreferably carried out in the presence of oxygen, most preferably in thepresence of air.

Further information on the copper and chromium compositions useful forthis invention is provided in U.S. Patent Application 60/706,159 filedAug. 5, 2005, and hereby incorporated by reference herein in itsentirety.

The calcined copper-substituted alpha-chromium oxide compositions usedin the present invention may be pressed into various shapes such aspellets for use in packing reactors or they may be used in powder form.

Typically, the calcined compositions will be pre-treated with afluorinating agent prior to use as catalysts for changing the fluorinecontent of halogenated carbon compounds. Typically this fluorinatingagent is HF though other materials may be used such as sulfurtetrafluoride, carbonyl fluoride, and fluorinated carbon compounds suchas trichlorofluoromethane, dichlorodifluoromethane,chlorodifluoromethane, trifluoromethane, or1,1,2-trichlorotrifluoroethane. This pretreatment can be accomplished,for example, by placing the catalyst in a suitable container which canbe the reactor to be used to perform the process in the instantinvention, and thereafter, passing HF over the dried, calcined catalystso as to partially saturate the catalyst with HF. This is convenientlycarried out by passing HF over the catalyst for a period of time, forexample, about 0.1 to about 10 hours at a temperature of, for example,about 200° C. to about 450° C. Nevertheless, this pretreatment is notessential.

Compounds that are produced in the chlorofluorination process in step(a) include the halopropanes CF₃CCl₂CClF₂ (CFC-215aa) and CF₃CCIFCCI₂F(CFC-215bb).

Halopropane by-products that have a higher degree of fluorination thanCFC-215aa and CFC-215bb that may be produced in step (a) includeCF₃CCl₂CF₃ (CFC-216aa), CF₃CClFCClF₂ (CFC-216ba), CF₃CF₂CCl₂F(CFC-216cb), CF₃CClFCF₃ (CFC-217ba), and CF₃CHClCF₃ (HCFC-226da).

Halopropane by-products that may be formed in step (a) which have lowerdegrees of fluorination than CFC-215aa and CFC-215bb includeCF₃CCl₂CCl₂F (HCFC-214ab) and CF₃CCl₂CCl₃ (HCFC-213ab).

Halopropene by-products that may be formed in step (a) includeCF₃CCl═CF₂ (CFC-1215xc), E- and Z-CF₃CCl═CClF (CFC-1214xb), andCF₃CCl═CCl₂ (CFC-1213xa).

Prior to step (b) CF₃CCl₂CClF₂ (CFC-215aa) and CF₃CCIFCCI₂F (CFC-215bb)(and optionally HF) from the effluent from step (a) are typicallyseparated from lower boiling components of the effluent (which typicallycomprise HCl, Cl₂, HF and over-fluorinated products such as C₃ClF₇ andC₃Cl₂F₆ isomers) and the under-fluorinated components of the effluent(which typically comprise C₃Cl₄F₄ isomers, CFC-213ab and/orunder-halogenated components such as C₃ClF₅ and C₃Cl₂F₄ isomers andCFC-1213xa). Underfluorinated and underhalogenated components (e.g.,CFC-214ab, CFC-1212xb, and CFC-1213xa) may be returned to step (a).

In one embodiment of the present invention, the CFC-216aa, and CFC-216baare further reacted with hydrogen (H₂), optionally in the presence ofHF, to produce 1,1,1,3,3,3-hexafluoropropane (HFC-236fa), and at leastone of 1,1,1,2,3,3-hexafluoropropane (HFC-236ea), hexafluoropropene(HFP) and 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea) as disclosed inU.S. Patent Application 60/706,161 filed Aug. 5, 2005.

In another embodiment of this invention, the reactor effluent from step(a) may be delivered to a distillation column in which HCl and any HClazeotropes are removed from the top of column while the higher boilingcomponents are removed at the bottom of the column. The productsrecovered at the bottom of the first distillation column are thendelivered to a second distillation column in which HF, Cl₂, CF₃CCl₂CF₃(CFC-216aa), CF₃CClFCClF₂ (CFC-216ba), CF₃CF₂CCl₂F (CFC-216cb),CF₃CClFCF₃ (CFC-217ba), and CF₃CHClCF₃ (HCFC-226da) and their HFazeotropes are recovered at the top of the column and CFC-215aa andCFC-215bb, and any remaining HF and the higher boiling components areremoved from the bottom of the column. The products recovered from thebottom of the second distillation column may then be delivered to afurther distillation column to separate the under-fluorinatedby-products and intermediates and to isolate CFC-215aa and CFC-215bb.

Optionally, after distillation and separation of HCl from the reactoreffluent of step (a), the resulting mixture of HF and halopropanes andhalopropenes may be delivered to a decanter controlled at a suitabletemperature to permit separation of a liquid HF-rich phase and a liquidorganic-rich phase. The organic-rich phase may then be distilled toisolate the CFC-215aa and CFC-215bb. The HF-rich phase may then berecycled to the reactor of step (a), optionally after removal of anyorganic components by distillation. The decantation step may be used atother points in the CFC-215aa/CFC-215bb separation scheme where HF ispresent.

In step (b) of the process of this invention, CF₃CCl₂CClF₂ (CFC-215aa)and CF₃CCIFCCI₂F (CFC-215bb) produced in step (a) are reacted withhydrogen (H₂) in a second reaction zone.

In one embodiment of step (b), a mixture comprising CFC-215aa andCFC-215bb is delivered in the vapor phase, along with hydrogen (H₂) to areactor containing a hydrogenation catalyst. Hydrogenation catalystssuitable for use in this embodiment include catalysts comprising atleast one metal selected from the group consisting of rhenium, iron,ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium, andplatinum. Said catalytic metal component is typically supported on acarrier such as carbon or graphite.

Of note are carbon supported catalysts in which the carbon support hasbeen washed with acid and has an ash content below about 0.1% by weight.Hydrogenation catalysts supported on low ash carbon are described inU.S. Pat. No. 5,136,113, the teachings of which are incorporated hereinby reference.

Of particular note are catalysts of palladium on carbon. Thehydrogenation of CFC-215aa and CFC-215bb to produce HFC-245fa andHFC-245eb is disclosed in International Publication No. WO 2005/037743A1, which is incorporated herein by reference.

The supported metal catalysts may be prepared by conventional methodsknown in the art such as by impregnation of the carrier with a solublesalt of the catalytic metal (e.g., palladium chloride or rhodiumnitrate) as described by Satterfield on page 95 of HeterogenousCatalysis in Industrial Practice, 2nd edition (McGraw-Hill, New York,1991). The concentration of the catalytic metal(s) on the support istypically in the range of about 0.1% by weight of the catalyst to about5% by weight.

The relative amount of hydrogen contacted with CFC-215aa and CFC-215bbin the presence of a hydrogenation catalyst is typically from about 0.5mole of H₂ per mole of trichloropentafluoropropane isomer to about 10moles of H₂ per mole of trichloropentafluoropropane isomer, preferablyfrom about 3 moles of H₂ per mole of trichloropentafluoropropane isomerto about 8 moles of H₂ per mole of trichloropentafluoropropane isomer.

Suitable temperatures for the catalytic hydrogenation are typically inthe range of from about 100° C. to about 350° C., preferably from about125° C. to about 300° C. Temperatures above about 350° C. tend to resultin defluorination side reactions; temperatures below about 125° C. willresult in incomplete substitution of Cl for H in the C₃Cl₃F₅ startingmaterials. The reactions are typically conducted at atmospheric pressureor superatmospheric pressure.

The effluent from the step (b) reaction zone typically includes HCl,unreacted hydrogen, HF, CF₃CH₂CHF₂ (HFC-245fa), CF₃CHFCH₂F (HFC-245eb),lower boiling by-products (typically including CF₃CH═CF₂ (HFC-1225zc),E- and Z-CF₃CH═CHF (HFC-1234ze), CF₃CF═CH₂ (HFC-1234yf), CF₃CH₂CF₃(HFC-236fa), CF₃CHFCH₃ (HFC-254eb), and/or CF₃CH₂CH₃ (HFC-263fb)) andhigher boiling by-products and intermediates (typically includingCF₃CH₂CH₂Cl (HCFC-253fb), CF₃CHFCH₂Cl (HCFC-244eb), CF₃CClFCH₂F(HCFC-235bb), CF₃CHClCHF₂ (HCFC-235da), CF₃CHClCClF₂ (HCFC-225da),and/or CF₃CClFCHClF (HCFC-225ba diastereromers)). The HFC-245fa andHFC-245eb are typically separated from lower boiling products and higherboiling products by conventional means (e.g., distillation).

In step (c) of the process, CF₃CH₂CHF₂ and CF₃CHFCH₂F produced in step(b) are dehydrofluorinated.

In one embodiment of step (c), a mixture comprising CF₃CH₂CHF₂ andCF₃CHFCH₂F, and optionally an inert gas, is delivered in the vapor phaseto a dehydrofluorination catalyst as described in U.S. Pat. No.6,369,284; the teachings of this disclosure are incorporated herein byreference. Dehydrofluorination catalysts suitable for use in thisembodiment include (1) at least one compound selected from the oxides,fluorides and oxyfluorides of magnesium, zinc and mixtures of magnesiumand zinc, (2) lanthanum oxide, (3) fluorided lanthanum oxide, (4)activated carbon, and (5) three-dimensional matrix carbonaceousmaterials.

The catalytic dehydrofluorination of CF₃CH₂CHF₂ and CF₃CHFCH₂F issuitably conducted at a temperature in the range of from about 200° C.to about 500° C., and preferably from about 350° C. to about 450° C. Thecontact time is typically from about 1 to about 450 seconds, preferablyfrom about 10 to about 120 seconds.

The reaction pressure can be subatmospheric, atmospheric orsuperatmospheric. Generally, near atmospheric pressures are preferred.However, the dehydrofluorination of CF₃CH₂CHF₂ and CF₃CHFCH₂F can bebeneficially run under reduced pressure (i.e., pressures less than oneatmosphere).

The catalytic dehydrofluorination can optionally be carried out in thepresence of an inert gas such as nitrogen, helium or argon. The additionof an inert gas can be used to increase the extent ofdehydrofluorination. Of note are processes where the mole ratio of inertgas to CF₃CH₂CHF₂ and/or CF₃CHFCH₂F is from about 5:1 to 1:1. Nitrogenis the preferred inert gas.

The products from the step (c) reaction zone typically include HF, E-and Z-forms of CF₃CH═CHF (HFC-1234ze), CF₃CF═CH₂ (HFC-1234ye),CF₃CH₂CHF₂, CF₃CHFCH₂F and small amounts of other products. UnconvertedCF₃CH₂CHF₂ and CF₃CHFCH₂F are recycled back to the dehydrofluorinationreactor to produce additional quantities of CF₃CH═CHF and CF₃CF═CH₂.

In another embodiment of step (c), the CF₃CH₂CHF₂ and CF₃CHFCH₂F aresubjected to dehydrofluorination at an elevated temperature in theabsence of a catalyst as disclosed in U.S. Patent Application No.60/623,210 filed Oct. 29, 2004, which is incorporated herein byreference. The reactor can be fabricated from nickel, iron, titanium, ortheir alloys, as described in U.S. Pat. No. 6,540,933; the teachings ofthis disclosure are incorporated herein by reference. A reaction vesselof these materials (e.g., a metal tube) optionally packed with the metalin suitable form may also be used. When reference is made to alloys, itis meant a nickel alloy containing form 1 to 99.9% (by weight) nickel,an iron alloy containing 0.2 to 99.8% (by weight) iron, and a titaniumalloy containing 72-99.8% (by weight) titanium. Of note is use of anempty (unpacked) reaction vessel made of nickel or alloys of nickel suchas those containing 40% to 80% nickel, e.g., Inconel™ 600 nickel alloy,Hastelloy™ C617 nickel alloy, or Hastelloy™ C276 nickel alloy.

Also of note is a reaction vessel where the reaction zone is lined withmechanically supported nickel as disclosed in U.S. Patent ApplicationPublication No. US 2005/0137430 A1 where the nickel is present in thereaction zone as a lining that is mechanically supported by a backingmetal material of construction that provides the strength and ductilityfor fabrication of the reaction zone and its use, the teachings of whichare incorporated herein by reference.

When used for packing, the metal or metal alloys may be particles orformed shapes such as perforated plates, rings, wire, screen, chips,pipe, shot, gauze, or wool.

The temperature of the reaction in this embodiment can be between about350° C. and about 900° C., and is preferably at least about 450° C.

In yet another embodiment of step (c), the CF₃CH₂CHF₂ and CF₃CHFCH₂F aredehydrofluorinated by reaction with caustic (eg. KOH). The vapor-phasedehydrofluorination reaction of CF₃CHFCHF₂ with caustic to produce bothCF₃CH═CF₂ and CF₃CF═CHF is disclosed by Sianesi, et. al., Ann. Chim.,55, 850-861 (1965) and the liquid-phase dehydrofluorination ofCF₃CH₂CHF₂ and CF₃CHFCH₂F in di-n-butyl ether, by reaction with caustic,to produce CF₃CH═CHF and CF₃CF═CH₂ is disclosed by Knunyants, et. al.,Izv. Akad. Nauk. SSSR, 1960, pp. 1412-1418, Chem. Abstracts 55, 349f theteachings of which are incorporated herein by reference.

In step (d) of the process, the CF₃CH═CHF and CF₃CF═CH₂ produced in (c)are recovered individually and/or as one or more mixtures of CF₃CH═CHFand CF₃CF═CH₂ by well known procedures such as distillation.

The reactor, distillation columns, and their associated feed lines,effluent lines, and associated units used in applying the processes ofthis invention should be constructed of materials resistant to hydrogenfluoride and hydrogen chloride. Typical materials of construction,well-known to the fluorination art, include stainless steels, inparticular of the austenitic type, the well-known high nickel alloys,such as Monel™ nickel-copper alloys, Hastelloy™ nickel-based alloys and,Inconel™ nickel-chromium alloys, and copper-clad steel.

The following specific embodiments are to be construed as merelyillustrative, and do not constrain the remainder of the disclosure inany way whatsoever.

EXAMPLES Catalyst Preparations Comparative Preparation Example 1Preparation of 100% Chromium Catalyst

A solution of 400 g Cr(NO₃)₃[9(H₂O)] (1.0 mole) in 1000 mL of deionizedwater was treated dropwise with 477 mL of 7.4M aqueous ammonia raisingthe pH to about 8.5. The slurry was stirred at room temperatureovernight. After re-adjusting the pH to 8.5 with ammonia, the mixturewas poured into evaporating dishes and dried in air at 120° C. The driedsolid was then calcined in air at 400° C.; the resulting solid weighed61.15 g. The catalyst was pelletized (−12 to +20 mesh, 1.68 to 0.84 mm))and 28.2 g (20 mL) was used in Comparative Example 1.

Preparation Example 1 Preparation of 99% Chromium/1% Copper Catalyst

To a one liter beaker containing 261.0 g Cr(NO₃)₃[9(H₂O)] (0.652 mole)and 1.46 g Cu(NO₃)_(2[)2.5H₂O]0.0063 mole) was added 100 mL of deionizedwater. The slurry was placed on a stirring hot plate in a fume-hood andheated while stirring until oxides of nitrogen started to evolve. Thebeaker containing the paste-like material was placed in a furnace in thefume-hood after removing the stirrer. The temperature of the furnace wasraised to 150° C. at the rate of 10 degrees/min and then to 550° C. atthe rate of 1 degree/minute. It was held at 550° C. for an additional 10hours. The resulting solid was pelletized (−12 to +20 mesh, 1.68 to 0.84mm)) and 12.6 g (8.0 mL) was used in Example 1.

Preparation Example 2 Preparation of 99% Chromium/1% Copper Catalyst

In a 2000 mL beaker was placed 400.2 g Cr(NO₃)₃[9(H₂O)] (1.0 mole) and1.64 g CuCl₂ (0.012 mole). To the solids was added 1000 mL of deionizedwater. The mixture was stirred and when the dissolution was complete,the pH of the solution was raised from 2.0 to 8.0 by drop-wise additionof 8 molar aqueous ammonium hydroxide. The precipitated slurry wasstirred for 24 hours at room temperature. It was then dried at 120-130°C. overnight and calcined at 450° C. for an additional 24 hours in air.The resulting solid was pelletized (−12 to +20 mesh, 1.68 to 0.84 mm))and 11.0 g (8.0 mL) was used in Example 2.

Preparation Example 3 Preparation of 99% Chromium/1% Copper Catalyst

In a 3000 mL beaker was placed 500.0 g Cr(NO₃)₃[9(H₂O)] (1.25 moles) and3.05 g Cu(NO₃)₂[2.5H₂O (0.013 mole). To the solids was added 1200 mL ofdeionized water. The mixture was stirred and when the dissolution wascomplete, the pH of the solution was raised from 2.4 to 8.5 by drop-wiseaddition of 300 mL of 8 molar aqueous ammonium hydroxide. Theprecipitated slurry was stirred for 24 hours at room temperature. It wasthen dried at 110-120° C. overnight and calcined at 500° C. for anadditional 24 hours in air. The resulting solid was pelletized (−12 to+20 mesh, 1.68 to 0.84 mm)) and 16.0 g (8.0 mL) was used in Example 3.

Preparation Example 4 Preparation of 98% Chromium/2% Copper Catalyst

Preparation Example 1 was substantially repeated except that the amountof chromium(III) nitrate was 258.0 g (0.645 mole) and the amount ofcopper (II) nitrate was 2.9 g (0.0125 mole). The resulting solid waspelletized (−12 to +20 mesh, 1.68 to 0.84 mm)) and 12.6 g (8.0 mL) wasused in Example 4.

Preparation Example 5 Preparation of 98% Chromium/2% Copper Catalyst

Preparation Example 2 was substantially repeated with 400.2 gchromium(II) nitrate (1.0 mole) and 3.31 g (0.0246 mole) copper(1)chloride. The solid, calcined in air at 450° C. for 24 hours, waspelletized (−12 to +20 mesh, 1.68 to 0.84 mm)) and 10.9 g (8.0 mL) wasused in Example 5.

Preparation Example 6 Preparation of 98% Chromium/2% Copper Catalyst

In a 3000 mL beaker was placed 500.0 g Cr(NO₃)₃[9(H₂O)] (1.1.25 mole)and 6.1 g Cu(NO₃)_(2[)2.5H₂O] (0.0262 mole). To the solids was added1200 mL of deionized water. The mixture was stirred and when thedissolution was complete, the pH of the solution was raised from 2.4 to8.2 by drop-wise addition of 300 mL 8 molar aqueous ammonium hydroxide.The precipitated slurry was stirred for 24 hours at room temperature. Itwas then dried at 110-120° C. overnight and calcined at 500° C. for anadditional 24 hours in air. The resulting solid was pelletized (−12 to+20 mesh, 1.68 to 0.84 mm)) and 14.9 g (8.0 mL) was used in Example 6 asthe catalyst.

Preparation Example 7 Preparation of 95% Chromium/5% Copper Catalyst

Preparation Example 1 was substantially repeated except that the amountof chromium(III) nitrate was 250.0 g (0.625 mole) and the amount ofcopper(II) nitrate was 7.3 g (0.314 mole). The resulting solid wascalcined at 550° C. overnight, pelletized (−12 to +20 mesh, 1.68 to 0.84mm)) and 11.9 g (8.0 mL) was used in Example 7.

Preparation Examples 8-9 Preparation of 95% Chromium/5% Copper Catalyst

Preparation Example 6 was substantially repeated except that the amountsof chromium(III) nitrate and copper(II) nitrate were adjusted to producea catalyst having a ratio of chromium to copper of 95/5. The solid driedat 110-120° C. overnight was divided into two portions. One portion wascalcined at 500° C. and another portion was calcined at 900° C. A 35.8 g(25.0 ml) portion, calcined at 500° C. and pelletized to −12 to +20mesh, was used in Example 8. Similarly a 48.1 g (25.0 ml) portion,calcined at 900° C. and pelletized to −12 to +20 mesh (1.68 to 0.84 mm),was used in Example 9.

Examples 1-9 and Comparative Example 1 General Procedure forChlorofluorination

A weighed quantity of pelletized catalyst was placed in a ⅝ inch (1.58cm) diameter Inconel™ nickel alloy reactor tube heated in a fluidizedsand bath. The tube was heated from 50° C. to 175° C. in a flow ofnitrogen (50 cc/min; 8.3(10)⁻⁷ m³/sec) over the course of about onehour. HF was then admitted to the reactor at a flow rate of 50 cc/min(8.3(10)⁻⁷ m³/sec). After 0.5 to 2 hours the nitrogen flow was decreasedto 20 cc/min (3.3(10)⁻⁷ m³/sec) and the HF flow increased to 80 cc/min(1.3(10)⁻⁶ m³/sec); this flow was maintained for about 1 hour. Thereactor temperature was then gradually increased to 400° C. over 3 to 5hours. At the end of this period, the HF flow was stopped and thereactor cooled to 300° C. under 20 sccm (3.3(10)⁻⁷ m³/sec) nitrogenflow. CFC-1213xa was fed from a pump to a vaporizer maintained at about118° C. It was combined with the appropriate molar ratios of HF andchlorine in a 0.5 inch (1.27 cm) diameter Monel™ nickel alloy tubepacked with Monel™ turnings. The mixture of reactants then entered thereactor. The HF/1213xa/chlorine molar ratio was 20/1/4 for all runs andthe contact time was 5 seconds for Examples 1-7, 30 seconds for Examples8-9 and 20 seconds for Comparative Example 1. The reactions wereconducted at a nominal pressure of one atmosphere. Analytical data foridentified compounds is given in units of GC area %. Small quantities ofother unidentified products were present.

General Procedure for Fluorocarbon Product Analysis

The following general procedure is illustrative of the method used foranalyzing the products of the chlorofluorination reactions. Part of thetotal reactor effluent was sampled on-line for organic product analysisusing a gas chromatograph equipped a mass selective detector (GC-MS).The gas chromatography was accomplished with a 20 ft. (6.1 m) long×⅛ in.(0.32 cm) diameter tubing containing Krytox® perfluorinated polyether onan inert carbon support. The helium flow was 30 mL/min (5.0(10)⁻⁷m³/sec). Gas chromatographic conditions were 60° C. for an initial holdperiod of three minutes followed by temperature programming to 200° C.at a rate of 6° C./minute.

Legend 214ab is CF₃CCl₂CCl₂F 215aa is CF₃CCl₂CClF₂ 215bb is CCl₂FCClFCF₃216aa is CF₃CCl₂CF₃ 216ba is CClF₂CClFCF₃ 216cb is CCl₂FCF₂CF₃ 217ba isCF₃CClFCF₃ 217ca is CF₃CF₂CClF₂ 225da is CF₃CHClCClF₂ 226da isCF₃CHClCF₃ 1214  is C₃Cl₂F₄ 1215xc is CF₃CCl=CF₂  

Chlorofluorination of 1213xa

The chlorofluorination of CFC-1213xa was carried out at varioustemperatures using catalysts prepared according to Catalyst PreparationExamples 1-9. The analytical results shown in Table 1 are reported as GCarea %.

TABLE 1 Cat Prep. T° C. 217ba 217ca 1215xc 226da 216aa 216ba 216cb 215aa215bb 214ab 1214 Ex.. No. 1 1 280 0.7 ND 0.9 2.4 14.4 4.8 0.6 63.4 8.53.2 0.3 320 3.4 0.3 1.0 2.4 36.3 14.8 1.2 38.9 1.4 ND ND 375 5.8 1.3 0.31.4 60.2 13.7 0.4 16.7 ND ND ND 2 2 280 0.4 ND 0.4 1.4 13.2 7.6 0.8 61.013.8 ND ND 320 1.4 0.4 0.2 1.4 31.1 23.3 1.0 41.1 0.1 ND ND 375 3.2 1.20.1 0.8 59.3 16.7 0.2 18.4 0.1 ND ND 3 3 320 2.4 0.4 0.3 0.8 32.8 26.62.0 33.5 1.1 ND ND 350 2.9 1.1 0.3 0.5 42.3 26.5 1.4 24.8 ND ND ND 3753.4 1.6 0.1 0.5 53.6 21.8 0.5 18.5 ND ND ND 4 4 280 0.2 ND 1.7 0.4 11.02.3 1.4 26.5 33.6 18.2 4.7 320 0.4 ND 0.9 0.5 21.0 12.1 1.9 41.8 20.40.8 0.1 350 0.5 0.2 0.6 0.4 28.1 21.2 2.5 36.8 9.4 0.1 ND 5 5 350 0.20.2 0.2 0.2 18.4 28.8 1.7 45.5 4.7 ND ND 375 0.3 0.5 0.2 0.1 24.4 30.61.6 41.4 0.7 ND ND 400 0.6 0.9 0.2 0.1 31.5 28.5 1.2 36.7 0.2 ND ND 6 6320 0.3 0.2 0.2 0.2 16.3 27.7 2.4 41.7 10.3 ND ND 350 0.9 0.8 0.3 0.226.7 33.1 2.0 33.9 2.0 ND ND 375 2.2 1.8 0.1 0.1 44.3 28.4 0.8 21.8 0.4ND ND 7 7 320 ND ND 1.1 0.1 8.5 4.3 1.5 39.6 36.0 7.8 1.0 350 0.1 0.10.9 0.1 10.9 10.4 2.0 42.9 30.9 1.6 0.3 400 0.1 0.1 0.6 ND 12.4 19.8 1.946.8 17.9 0.3 0.1 8 8 280 ND ND 0.8 ND 3.5 0.9 0.5 26.7 36.0 26.5 4.6320 ND ND 1.9 ND 6.7 11.8 0.8 49.8 27.2 0.7 0.3 425 ND ND 0.9 0.2 5.525.7 0.7 59.1 5.9 0.1 0.2 9 9 280 ND ND 0.3 ND 2.9 0.4 0.6 20.2 47.325.9 1.9 320 ND ND 0.3 ND 3.8 1.4 1.0 29.3 48.4 14.3 1.1 425 ND ND 0.3ND 5.1 12.8 1.4 50.8 28.1 0.6 0.2 Comp. 320 12.4 ND 0.2 2.4 30.3 18.0 ND34.5 ND ND ND Ex 1 ND = Not Detected

Examination of the data shown in Examples 8 and 9 above show that theamount of CF₃CCl₂CClF₂ and CF₃CCIFCCI₂F can be maximized relative toCF₃CCl₂CF₃ and CF₃CClFCClF₂ by controlling the operational variables byusing the catalysts of this invention. The CFC-215aa and CFC-215bbproduced above may be hydrogenated to produce CF₃CH₂CHF₂ and CF₃CHFCH₂F,respectively, in a manner analogous to the teachings of InternationalPublication No. WO 2005/037743 A1. The CF₃CH₂CHF₂ and CF₃CHFCH₂F maythen be dehydrofluorinated to CF₃CH═CHF and CF₃CF═CH₂, respectively, inaccordance with the teachings described in U.S. Pat. No. 6,369,284. TheCF₃CH═CHF and CF₃CF═CH₂ may be recovered individually or as mixtures ofCF₃CH═CHF and CF₃CF═CH₂ by procedures well known to the art.

1. A process for the manufacture of at least one compound selected fromthe group consisting of 1,3,3,3-tetrafluoropropene and2,3,3,3-tetrafluoropropene, comprising: (a) reacting hydrogen fluoride,chlorine, and at least one halopropene of the formula CX₃CCl═CClX,wherein each X is independently selected from the group consisting of Fand Cl, to produce a product comprising CF₃CCl₂CClF₂ and CF₃CClFCCl₂F,wherein said CF₃CCl₂CClF₂ and CF₃CClFCCl₂F are produced in the presenceof a chlorofluorination catalyst comprising at least onechromium-containing component selected from (i) a crystallinealpha-chromium oxide where at least 0.05 atom % of the chromium atoms inthe alpha-chromium oxide lattice are replaced by divalent copper, and(ii) a chromium-containing composition of (i) which has been treatedwith a fluorinating agent; (b) reacting CF₃CCl₂CClF₂ and CF₃CClFCCl₂Fproduced in (a) with hydrogen to produce a product comprising CF₃CH₂CHF₂and CF₃CHFCH₂F; (c) dehydrofluorinating CF₃CH₂CHF₂ and CF₃CHFCH₂Fproduced in (b) to produce a product comprising CF₃CH═CHF and CF₃CF═CH₂;and (d) recovering at least one compound selected from the groupconsisting of CF₃CH═CHF and CF₃CF═CH₂ from the product produced in (c).2. The process of claim 1 wherein the halopropene reactant is contactedwith Cl₂ and HF in a pre-reactor.
 3. The process of claim 1 wherein thehalopropene reactant is contacted with HF in a pre-reactor.
 4. Theprocess of claim 1 wherein the reaction of (b) is conducted in areaction zone containing a hydrogenation catalyst at a temperature offrom about 100° C. to about 350° C.
 5. The process of claim 1 whereinthe reaction of (c) is conducted at an elevated temperature in theabsence of a catalyst at a temperature of about 350° C. to about 900° C.6. The process of claim 1 wherein the reaction of (c) is conducted at anelevated temperature in a reaction zone containing a dehydrofluorinationcatalyst at a temperature of about 200° C. to about 500° C.
 7. Theprocess of claim 1 wherein the amount of copper relative to the total ofchromium and copper in the catalyst composition is from about 1 atom %to about 5 atom %.